The invention relates to a wiper blade made of rubber.
Complex demands are placed on wiper blade materials with regard to mechanical properties and also the resistance to external influences: wiper blade materials must be flexible, slide easily over the windshield, and be resistant to external influences, in particular oxidation (ozone cleavage), mineral oil, and chemicals that are contained, for example, in wiper fluid.
As a rule, wiper blade materials are rubbers, i.e. vulcanized natural and/or synthetic rubbers (see Rxc3x6mmp Chemie Lexikon 9th edition, p.1668).
In order to improve the sliding properties of rubbers as wiper blade materials, the proposal has been made, for example, to coat the wiper surface, chlorinate it, or apply sliding powder to it such as molybdenum sulfide.
The wiper rubber according to DE-C-35 27 093 is comprised predominantly of EPDM, i.e. of ethylene-propylenediene-terpolymer. In EPDM, the unsaturated sites are disposed outside the main polymer chain and therefore EPDM cannot be halogenated. In addition, EPDM is not resistant to mineral oil and chemicals from the wiper fluid. In order to improve the sliding properties and the resistance of the wiper blade comprised predominantly of EPDM, therefore, according to DE-C-35 27 093, segments of chlorinated diene-type rubber are deposited on a matrix of EPDM, at least in the regions that slide on the surface of the windshield during proper use. The wiper blade has the disadvantage of a relatively complex construction of layers of different rubber materials.
Accordingly, it is object of present invention to provide a wiper blade which avoids the disadvantages of the prior art.
In keeping with these objects, one feature of present invention resides, briefly stated, in a wiper blade, in which the head piece is essentially made of a diene-type rubber and the flexing piece and wedge are essentially made of chloroprene rubber.
The wiper blade with these features of the main claim has the advantage over the prior art that a favorable wiping quality is achieved with a simple design.
The head piece made of a diene-type rubber can be halogenated, which produces favorable sliding properties and smooth running in the regions in which the wiper blade cooperates with the bracket claws and the spring strip of the metallic retainer and also produces a harder surface.
For the flexing piece and the wedge of the wiper blade, chloroprene rubber is used according to the invention, which will be referred to below by the internationally standard abbreviation CR. As a result, a favorable wiper quality is achieved in a simple and inexpensive manner.
CR combines favorable mechanical properties with high resistance to the influences of weather, aging, chemicals, and temperature.
Mechanical properties of CR that are important for its use as a wiper blade material include favorable elastic properties, lowest compression set in the temperature range from xe2x88x9210xc2x0 C. to 120xc2x0 C., i.e. in the relevant temperature range for use as a wiper blade, as well as very favorable wear resistance which is only achieved otherwise through the use of expensive synthetic specialized rubber types.
In addition to the favorable mechanical properties, it has a high resistance to external influences: high weather resistance and resistance to ozone cleavage, which in contrast to other rubber types, can still be improved significantly through the addition of antioxidants and ozone inhibitors, low swelling, and high resistance to chemicals that are contained, for example, in wiper fluid, significantly higher resistance to mineral oil in comparison to vulcanizates based on natural rubber, as well as excellent temperature resistance which exceeds that of conventional vulcanized rubbers e.g. based on natural rubber, butadiene rubber, or styrene-butadiene rubber. The long-term temperature resistance of CR is approx. 80xc2x0 C.
CR thus has a combination of properties which are important for the use as a wiper blade material, at a significantly lower price in comparison to specialized rubber types.
Advantageously, the region of the head piece that adjoins the flexing piece is made of the same rubber material as the wedge and the flexing piece, i.e. is made of CR. This achieves a better anchoring of the parts made of CRxe2x80x94flexing piece and wedgexe2x80x94in the head piece which is comprised essentially of the diene-type rubber.
The diene rubber of the head piece is advantageously halogenated, preferably chlorinated. This improves the surface hardness and the sliding ability in relation to the metallic retaining elements such as claw brackets and spring strips.
The rubber material for the head piece is essentially a diene rubber, wherein preferably inexpensive, commercially available rubber types are used, for example natural rubber and/or butadiene rubber and/or styrene-butadiene rubber.